Process for treating hydrocarbons



Patented Jan. 20, 1948 2,434,839 PROCESS FOR TREATING HYDROCARBONS Orris L. Davis, Oakland, and Alan C. Nixon, Berkeley, Calif assignors to Shell Development Company. San Francisco, Calif., a corporation of Delaware No Drawing.

Original application October 27,

1948, Serial No. 508,089. Divided and this application June 10, 1946, Serial No. 675,838

13 Claims.

This invention deals with a method for improving the rate of separation of aqueous alkaline treating solutions or solutions from hydrocarbons or 01' facilitating steam stripping of the resulting tat alkaline solution, it the latter is desired, or both.

It is well known that hydrocarbon oils are mixtures 01' hydrocarbons and may contain compounds of many diflerent degrees of saturation, such as paraflins, oieflns, polyolefins, acetylenes, naphthenes. or aromatics. It i also known that hydrocarbon oils frequently contain weak acids e. g., having dissociation constants below about such as hydrogen sulfide, mer'captans, alkyl phenols, etc. It is often desirable to treat such hydrocarbon mixtures to separate them into hydrocarbons of different degrees of saturation, or to purify particular hydrocarbons, such as benzene, toluene. xylene. butylenes, butadiene, isoprene, ethylene. acetylene. etc.; or to remove weak acids of the type mentioned above from such hydrocarbons or mixtures.

One method oi carrying out such a separation or purification is by extracting one or more of the components with an alkaline solution, which has a preferential solvent power for one or more oi the components of the mixture, and thereafter separating the resulting alkaline solution from the dissolved portion of the mixture. The extraction may be either by liquid-liquid or by vapor-liquid contact, including extractive distillation. (In order to achieve separation by ex tractive distillation the two or more compounds generated such as by steam stripping, air blowing or washing with a suitable wash liquid, etc., and the regenerated solution is then re-used for treatment of further quantities of the original mixture.

The mixtures to which this invention is applicable are either normally liquid or normally gaseous and preferably have an end boiling point of below about 200 0. They are comprised of hydrocarbons and must be substantially free from sulfate ester acids, sulionic acids, or other relatively strong acids because of the effect of these acids upon the alkaline treating solution by permanently poisoning or neutralizing it.

Aqueous alkaline treating solutions which may be employed must be stable and inert so as not to react irreversibly with the components of the mixture under the conditions of the process; they must have a greater solvent power for some components than for others; and they must be separable from the dissolved components by physical means such as, by fractional distillation and/or washing-out, either while they are in the form originally absorbed or else after they have been changed chemically by a simple operation such as air oxidation. If employed in liquid extraction, they must be only partially miscible with mixtures to be extracted.

to be separated from one another should as a rule boil not more than about 20 C. apart and preferably not more than about 10 C. apart.) These extractions are normally carried out in apparatus permitting contact of the alkaline treating solution and the mixture containing the hydrocarbons, usually by counter-current flow, either through a packed or plate column, or through a series of mixers and settlers. whereby two end phases are produced and separated, one of which is an extract comprising the fat alkaline treating solution containing the extracted portion of the mixture, and the other of which is the raflinate portion of the mixture. These two phases may be both liquid or one may be liquid and the other ma be a vapor. For reasons of economy, the fat alkaline solution is usually re- Some specific examples of alkaline treating sol'utions for the separation of unsaturated hydrocarbons from mixtures containing them are: solutions of complex compounds of ammonia and salts of univalent heavy metals from groups I and II of the periodic table, such as copper, silver, gold, mercury, etc., chlorides, nitrates, cyanides, acetates, etc., in water. In the extraction of weak acids normally associated with petroleum oils, alkaline treating solutions, such as tripotasslum phosphate, sodium phenclate, sodium borate, sodium or potassium carbonate, etc., or strong solutions of alkaline metal hydroxides, preferably having concentrations of 25 to 50% or alkaline solutions containing solutizers may be employed.

Solutizers are known a organic substances which when in the liquid state are solvents for weak organic acids, are substantially insoluble in water-immiscible liquids, are soluble in aqueous strong bases, are chemically inert to the action of said bases even at elevated temperatures, and

liquid-liquid treating,

have boiling temperatures preferably substantially higher than water. Solutlzers are used to enhance the extractive powers of aqueous alkaline solutions for weak organic acids such as mercaptans and phenols. The solutizer process and the various solutizers have been described in a series of patents and patent applications as well as in the general literature, for example, in the Yabrofl' et a1. U. S. Patents 2,149,379, 2,149,380, 2,152,166, 2,152.720, 2,152,723, 2,164,851, 2,186,398, 2,202.039; applications Serial Numbers 255.684, filed February 10, 1939: 271.962, filed May 5, 1939: Reflner and Natural Gasoline Manufacture, May 1939, pages 171-176. and March 1940, pages 73- 76: Industrial Engineering and Chemistry, volume 32. pages 257-262. February 1940. etc.

In choosing one of the above alkaline treating solutions, sight must not be lost of the boiling temperature requirements relative to the boiling temperature of the mixtures. For example, in vapor-liquid extraction, it is important that the solvent chosen have a boiling temperature higher than that of the mixture to be treated, and in the specific case of extractive distillation, it is desirable that the boiling temperature of the solvent be not less than about 50 C. higher than the boiling temperature of the mixture. Accordingly, the particular treating agent to be employed necessarily depends upon both the boiling temperature of the mixture to be treated, and the type of process to be used in the treatment.

Unfortunately, processes of this type often produce foam and/or emulsions which greatly reduce the maximum throughput of a given treating unit. Emulsions. if formed, occur in and foamin may occur in vapor-l ouid treating. Foaming may also occur if distillation, steam stripping, air blowing, etc., is employed as a means for recovering the alkaline treating solution from the extract or rainnate.

The nature of the substances responsible for difllculties is not definitely established. It is believed though. that foam and emulsions are produced by small amounts of impurities, such as compounds related to gasoline gums or similar resinous materials formed by reaction of some of the component of the hydrocarbon mixtures with themselves or with the alkaline treating solution or a component thereof, particularly in the presence of oxygen. In many cases it is impossible to keep air away from such mixtures. since small quantities easily leak through joints of pumps and valves, etc. Thus. most hydrocarbon oils contain small but definite amounts of dissolved oxygen. In the case of treating solutizer solutions with alkaline solutions containing phenolates, a phenol type resin may be formed, for instance, by the interaction of mercaptans, aldehydes or other impuritie in the mixture treated.

Accordingly, it is the purpose of this invention to provide means for improvin the rate of separation of aqeuous alkaline treating solutions from the hydrocarbons which are being treated. Another purpose is simultaneously or independently to reduce the foaming tendency of the treating solution for example, when it is being regenerated by steam stripping. Still another purpose is to provide means for preventing the formation of emulsions caused by the presence of emulsifiers in the treating solution, particularly those containing impurities which readily react to form emulsifiers. It is yet another purpose to provide a remedy for breaking emulsions formed in such treating processes.

It has been discovered that the addition of relatively small amounts of a stable organic surface-active agent which contains at least 8 carbon atoms per molecule and has a molecular weight of below about 1000 (preferably below about 600) and which is soluble in, or spontaneously forms, a colloidal dispersion in the alkaline treating solution, results not only in reducing foaming and in an improved rate of separation, but also in effective and rapid breaking of emulsions which may form between the two phases produced in the process. The term "surface-active agent as herein used refers to substances which are capable of doing work at the interfaces, i. e., produce a marked change in interfacial tensions. It is important that the agent be readily and completely dispersed through the treating solution so as to be continuously and evenly effective throughout the entire zone of contact.

The agents should be reasonably stable toward the action of oxygen in the presence of caustic alkali and at elevated temperatures of steaming if steam regeneration is employed as part of the process.

In a regenerative process wherein the spent treated solution is continuously regenerated and recirculated for further contact with the mixture to be treated, it is desirable but not essential, that the surfaceactive agents, in order to be more or less permanently useful, should not be extracted from the treating solution when the latter is contacted with the hydrocarbon mixture. The presence of the agent in either of the separated components of the mixture may be undesirable, as it may interfere with their intended uses.

In some cases, it may be desirable to remove these agents from the treating solution in which case they should have a property which makes possible such separation.

The organic surface-active agents of this invention are anion active and cation active compounds. These are organic compounds containing at least one atom of oxygen; and aliphatic alcohols having between 8 and 14 carbon atoms per molecule. Such surface-active compounds may be generally represented by the formula RY, wherein R is an organic radical and Y is a polar radical containing an atom of oxygen.

Those which are more effective for breaking and reducing foams are the alcohols having from 8 to 14 carbon atoms such as octyl, nonyLdecyl, undecyl, dodecyl, etc., alcohols. Alcohols containing less than 8 carbon atoms per molecule such as isoamyl alcohol and n-hexyl alcohol and those containing more than 14 carbon atoms such as cetyl alcohol are substantially ineffective for the described purpose.

Amounts of the surface-active agents which need to be added to improve the rate of settling or breaking of the emulsion or foam or both, are insufficient to materially affect the action of the treating agent. This amount may vary between about 001% and 1%, and preferably between about .001% and .1% by volume of the treating agent. The different types of treating agents are capable of dissolving difierent amounts of the surface-active agents and different mixtures may require different amounts to reduce foaming and/or emulsification. This is probably due to the difference in reactivity of the ions of the re spective agents and their effect on the hydrocarbon mixtures treated. Therefore. actual laboratory tests within the above limitations may be required to accurately determine the amount the agent or combination of agents ior'the most effective separation 01' the given mixture with a given alkaline treating solution.

It is'desirable that the beneficial effect of the agent shall not be restricted to and be dependent on a specific range 01 concentration substantially narrower than the limits indicated above-that is to say, there should not be a sudden reversal of the beneficial effect, 1. e., an increase in the emulsiflcation of foaming tendencies or both, of the extracting solution upon addition of a slight excess of the agent over the optimum quantity. 0n the contrary, the beneficial effects should extend over substantially the entire range of concentration indicated,'and changes in the effects due to deviations from the optimum concentration should be only matters of degree.

Example In the table below, effects of a number of representative surface-active agents are shown in a spent or contaminated aqueous copper ammonium acetate solution which when fresh had the following composition: .25 moi/liter of cupric ions, 2.93 mols/liter of cuprous' ions, 10.4'

mols/liter of ammonia, and 4.0 mols/lit'er of acetic acid. Samples. of this spent solution were subjected to an emulsion test in which they were agitated with an equal amount by volume of ter-' tiary amylenes at a temperature of about F..

The resulting emulsion was then allowed to settle and the time required for substantially complete separation was noted and whether or not at the end of the settling a residual rag (large globules of hydrocarbon surroundedby'thin films of solution) was left at the interface between the solvent phase and the hydrocarbon phase. The reinsoluble in said mixture, and being an unsubstituted aliphatic alcohol having between 8 and 14 carbon atoms per molecule.

2. The process of claim 1, wherein said mixture is a gasoline distillate.

3. The process of claim 1, wherein said mixture contains C4 dioleflns.

4. The process of claim 1, wherein said treating process is a liquid-liquid phase separation process.

5. The process of claim 1, wherein the treating process is a vapor-liquid phase separation process.

- 6. The process of claim 1, wherein the surface-, active agent is a. cation-active agent.

7. The process of claim 1, wherein said mixture contains diolefins and said alkaline treating solutionis an aqueous alkaline copper ammonium acetate solution.

8. The process of claim 1, wherein the amount oi the said surface-active agent is between'about .coo1% and .1 by volume of said mixture.

9. The process of claim 1, wherein the amount of the said surface-active agent is between about 001% and .l% by volume of said mixture 1 10. The process 01' claim 1, wherein said disperslon is a foam.

11, In a process Ior treating a hydrocarbon fraction with an aqueous copper ammonium acetate solution, whereby two phases are produced,

in which process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a'result of reactions oi. unsaturates in said mixture with each other and with oxygen, the method of preventing such a dispersion which comprises effecting said treating in the presence of a relatively small amount of an unsubstituted aliphatic alcohol having between 8 and 14 carbon atoms per molecule, said alcohol being miscible in said aqueous copper ammonium suits were as follows: 40 acetate solution.

Gone. in Settling Vol. oi gm.l100 cc. Time in Residual Remarks Solvent Minutes Rag Organic Surface-active Agent:

Fresh Solution 0 1% 0 No foam. Spent Solution 0 35 9 Stable loam. Alcohols:

Decyl Alcohol 1 30 1 No loam. Do 01 30 1 Do. Do 0025 Do. Lauryl Alcohol. 01 l2 10 Light foam. 2-ethyl hexanol l 1 i5 10 No foam.

This application is a true division of the copending application, Serial No. 508,089, filed 0ctober 27, 1943, issued November 12, 1946, as U. S. Patent No. 2,411,083.

We claim as our invention:

1. In a process for treating a mixture comprising hydrocarbons with an aqueous alkaline treating solution of a compound selected from the group consisting of alkaline alkali metal compounds and alkaline ammonia compounds, whereby two phases are produced, in which process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a result of reactions of components of said mixture, the method of reducing the stability of such a dispersion which comprises effecting said treating in the presence of a relatively small amount of not more than about 1% by volume of said mixture of an organic surface-active agent having at least 8 carbon atoms per molecule and a molecular weight below 1000. said agent being soluble or spontaneously dispersible colloidally in 12. In a process for purifying a hydrocarbon mixture containing a C4 diolefln by liquid-liquid phase treatment with an aqueous alkaline solution of a complex compound of ammonia with a copper salt, whereby two phases are produced, in which process a relatively stable dispersion of one phase in the other is produced by the action of impurities formed as a result of reactions of components of said mixture, the method of reducing the stability of such a dispersion which comprises effecting said treating in the presence of between about 0.0001% and 1% by volume of said mixture of an unsubstituted aliphatic alcohol having between 8 and 14 carbon atoms per molecule.

13. In a process for treating a hydrocarbon fraction with an aqueous copper ammonium acetate solution, whereby two phases are produced, in which process a relatively stable dispersion 01' one phase in the other is produced by the action of impurities formed as a result of reactions of unsaturates in said mixture with each other and with oxygen, the method of preventing such a 7 8 1n the presence of between about 0.0001% and 1% of an unsubstituted aliphatic alcohol having be- UNITED STATES PATENTS tween 8 and 14 carbon atoms per molecule. Number Name Date QRRIS DAVIS, 2,152,723 Yabrofl (B) Apr. 4, 1939 ALAN c NIXON, 5 2,212,107 Yabrofl (A) Aug. 20. 1940 2,281,347 Blair Apr. 28, 1942 REFERENCES CITED The following references are of record in the file of this patent: 

